The Hydrogen Intensity and Real-time Analysis eXperiment (HIRAX) will measure the HI density field over the redshift range \(0.8 < z < 2.5\) , bracketing the redshift at which dark energy begins to affect the dynamics of the universe.
The large daily survey area (approximately 1,000 deg\(^2\) ), and real-time processing capabilities of HIRAX will also make it an effective observatory for detecting and monitoring radio transients, such as fast radio bursts (FRBs) and pulsars[1]}, [2]}, [3]}, [4]}, [5]}. The Southern Hemisphere survey location also provides overlap with the survey fields of cosmology surveys undertaken by ACT[6]}, SPT[7]}, DESI[8]}, and the Vera Rubin Observatory[9]}, allowing for significant cross correlation studies. HIRAX will also deliver a blind HI 21 cm line survey at \(0.8 < z < 2.5\) . This will complement the MeerKAT Absorption Line Survey (MALS; \(0 < z < 1.4\) ) by extending the exploration of cold atomic gas in the circum-galactic and inter-galactic medium to higher redshifts[10]}.
